Insurgents ambushed a police vehicle in southwest Afghanistan, and the three-hour gunbattle that followed left four policemen dead. Two other police officers were wounded in Thursday's clash in Nimroz province, said Gen. Mohammad Ayub Badakhshi, the provincial police chief. Reinforcements were sent to assist, but the insurgents escaped, Badakhshi said. Afghanistan has seen a massive spike in insurgency-related violence, with more than 6,500 people dead in 2007, according to an Associated Press tally of figures from Afghan and Western officials.